Long-term and Short-term Debt (Narrative) (Details) - USD ($) $ in Millions	2 Months Ended	10 Months Ended	12 Months Ended
	Dec. 31, 2017	Oct. 31, 2017	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Nov. 01, 2017	Aug. 02, 2017	Jul. 21, 2017	Jun. 30, 2017	Apr. 30, 2017	Dec. 11, 2015	Nov. 13, 2015	Mar. 05, 2015
Debt Instrument [Line Items]
Other Short-term Borrowings	$ 377		$ 377	$ 142
Short-term Debt, Weighted Average Interest Rate, at Point in Time	2.41%		2.41%	1.32%	0.15%
Debt Instrument, Face Amount	$ 3,200		$ 3,200	$ 3,200
Debt Issuance Costs, Gross												$ 10
Debt Instrument, Unamortized Discount (Premium) and Debt Issuance Costs, Net	95		95	103
Long Term Debt Aggregate Maturities, Year One	1,100		1,100
Long Term Debt Aggregate Maturities, Year Two	1,000		1,000
Long Term Debt Aggregate Maturities, Year Three	540		540
Long Term Debt Aggregate Maturities, Year Four	999		999
Long Term Debt Aggregate Maturities, Year Five	846		846
Long-term Debt, Maturities, Repayments of Principal after Year Five	11,200		11,200
Interest Expense, Debt			841	874	$ 890
Senior notes
Debt Instrument [Line Items]
Long-term Debt, Gross	14,685		14,685	15,597
Debt Instrument, Unamortized Discount (Premium) and Debt Issuance Costs, Net	86		86	92
Other Notes MPEH [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount											$ 350
Line of Credit Facility, Maximum Borrowing Capacity	75		75
Debt Issuance Costs, Gross											6
Debt Instrument, Description of Variable Rate Basis		three-month LIBOR plus 3.70%
Other Notes [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross	578		578	420
Debt Instrument, Unamortized Discount (Premium) and Debt Issuance Costs, Net	$ 4		$ 4	5
Senior Debt 500 Million November 2025 [Member] | Senior notes
Debt Instrument [Line Items]
Debt Instrument, Face Amount												$ 500
Debt Instrument, Maturity Date			Nov. 13, 2025
Debt Instrument, Interest Rate, Stated Percentage												3.60%
Senior Debt 750 Million May 2046 [Member] | Senior notes
Debt Instrument [Line Items]
Debt Instrument, Face Amount												$ 750
Debt Instrument, Maturity Date			May 13, 2046
Debt Instrument, Interest Rate, Stated Percentage												4.60%
Senior Debt $500 Million March 2025 [Member] | Senior notes
Debt Instrument [Line Items]
Debt Instrument, Face Amount													$ 500
Debt Instrument, Maturity Date			Mar. 01, 2025
Debt Instrument, Interest Rate, Stated Percentage													3.00%
Senior Debt $1.0 Billion March 2045 [Member] | Senior notes
Debt Instrument [Line Items]
Debt Instrument, Face Amount													$ 1,000
Debt Instrument, Maturity Date			Mar. 01, 2045
Debt Instrument, Interest Rate, Stated Percentage													4.05%
Senior Debt March 2015 [Member]
Debt Instrument [Line Items]
Debt Issuance Costs, Gross													$ 12
Amendment [Member] | Other Notes MPEH [Member]
Debt Instrument [Line Items]
Debt Instrument, Maturity Date	Nov. 15, 2022
Line of Credit Facility, Maximum Borrowing Capacity						$ 75					$ 100
Debt Issuance Costs, Gross						$ 1
Debt Instrument, Description of Variable Rate Basis	three-month LIBOR plus 3.25%
Securities Sold under Agreements to Repurchase [Member]
Debt Instrument [Line Items]
Other Short-term Borrowings	$ 374		$ 374	$ 133
Affiliated Entity [Member] | Other Notes [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross	139		139
Brighthouse Financial, Inc [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount							$ 500
Line of Credit Facility, Maximum Borrowing Capacity								$ 600	$ 536	$ 3,000
Committed Credit Facility Six [Member]
Debt Instrument [Line Items]
Letters of Credit Outstanding, Amount	2,354		2,354
Line of Credit Facility, Maximum Borrowing Capacity	2,896		2,896
Committed Credit Facility Six [Member] | Brighthouse Financial, Inc [Member]
Debt Instrument [Line Items]
Letters of Credit Outstanding, Amount	2,400		2,400
Line of Credit Facility, Maximum Borrowing Capacity	$ 2,900		$ 2,900